The invention relates to methods and devices for producing stacks composed of printed products which are supplied continuously while essentially positioned upright with the aid of a first conveying device and in an overlapping flow to a substantially horizontally extending stack support and which form a stack while lined up at least approximately positioned upright. The stack that is positioned on the stack support is conveyed with the aid of a second conveying device in a forward-feed direction and at a forward-moving speed and, in the process, is supported along one leading stack end against a supporting device that also moves along.
A method and device for producing stacks composed of print products are generally disclosed in the art, for example in European patent documents EP 0623542, EP 0872443 and EP 1405809. Stacks of this type, also called bundles, are held together with the aid of end boards and strapping and have long proven themselves in the process of removing printed sheets from printing presses and preparing them for the further processing.
Stacking thick printed sheets, for example sheets containing 100 or more pages, often causes a comparatively strong spreading out or expansion of the sheets towards end of stack, which are positioned on their backs during the conveying for the stack formation. In particular with folded printed products where the folding edges respectively form the backs, this can make the stack formation considerably more difficult. In addition, these printed products can be damaged during the stack formation because of the comparatively high friction.
An arrangement said to be especially suitable for such printed products is disclosed in European patent document EP 1950159, in particular for products that are stitched or stapled along the fold, wherein these printed products can include newspapers, magazines or brochures. To simplify the stack forming process, it is proposed to divide the stack into a plurality of stack sections and to arrange these sections offset against each other. For the offset arrangement of a stack, a displacement device is required which engages in the stack support and is embodied, for example, as graduated conveying belt. A stack composed of offset stack sections, however, requires considerably more space, and the production thereof is clearly more involved than that of a traditional stack.
The method according to the European patent document EP 1350750 is intended to facilitate the forming stacks composed of printed products. For this, the sheet-metal guides arranged in the region above the area where the printed products arrive on the stack support are respectively provided with a region that projects in stacking direction and which functions to redirect the printed products into stacking direction during the feeding to the stack support. This is operative to increase the inherent stability of the printed products during the intake as well as to provide more space for the newly supplied printed products. However, this method has the disadvantage that the friction is increased between the printed products, thus also increasing the risk of damage to the products and/or blurring of the print color. A compacting device for compacting the downstream-directed portion of the stack is furthermore arranged in stacking direction at a distance to the area of impact for the printed products, which acts to accelerate two opposite-arranged edge regions of the of the printed products in stacking direction. A brush roller is also arranged, according to one embodiment, on both sides above the upstream, non-compressed portion of the stack which promotes the conveying.